402 
INTRODUCTION TO THE 
sary modifications, which have served as the basis of other subsequent classifications. 
He at first characterized insects from other invertebrated animals, by more rigorous 
characters than had been before employed,— namely, a knotted or ganglionated nervous 
chord, extending down the body, and articulated limbs. Linnseus terminated his class 
of insects with those which are destitute of wings, although some of them — as the 
crabs and spiders — are, in respect to their organic systems, the most perfectly organized 
{ks plus parfaits) of the class, and consequently the nearest to the molluscous animals. 
This arrangement is therefore opposed to the natural system; and M. Cuvier, by placing 
the Crustacea at the head of the class, succeeded by the other apterous insects, has 
rectified the method in a point where the series was in opposition to the scale formed 
by nature. 
In his Legons d’ Anatomie Comparee, the class of insects, after the removal of the 
Crustacea, was divided into nine orders, founded upon nature, or the functions of their 
mouth-organs, and the variations in their wings, thus uniting the principles of the 
Linnsean and Fabrician arrangements. [1st. Those with maxillae, five orders : Gnath- 
aptera (including the majority of the Linnaean Aptera, after the removal of the Crustacea), 
Neuroptera, Hymenoptera, Coleoptera, and Orthoptera ; and, 2nd, those without max- 
illae, four orders : Hemiptera, Lepidoptera, Diptera, and Aptera.] The groups esta- 
blished by Cuvier in his Gnathapterous order are nearly identical with those which I 
proposed in a Memoir presented to the Societe Philomatique, in April, 1795, and in my 
Precis des Caracteres Ge'neriques des Insectes, in which I divided the Linnaean Aptera 
into seven orders: — 1. Suctoria; 2. Thysanura; 3. Parasita; 4. Acephala (the Arach- 
nides palpistes of Lamarck); 5. Entomostraca ; 6. Crustacea; 7. Myriapoda. 
Lamarck’s arrangement of the Linnaean Aptera appears, however, to make the nearest 
approach to a natural system; and we have adopted it, with certain modifications, which 
we wiU now explain. With him, I divide the Linnaean insects into three classes : — 
Crustacea, Arachnida, and Insecta ; but I do not employ the characters derived 
from metamorphosis ; — these, although natural, and already employed by De Geer, not 
being classical (classique), presupposing the observation of the animal in its different 
states, which has been so much neglected. I have not, however, entirely neglected 
these characters ; and, indeed, a Memoir which I have prepared upon the metamor- 
phoses of insects, not yet published, has been resorted to in the general observations 
upon the different groups. 
In the class Crustacea, I have established five apparently natural orders, founded 
upon the situation and form of the branchiae, the manner in which the head is articu- 
lated with the thorax, and the mouth-organs ; and I have terminated this class, like 
Lamarck, with the Branchiopoda, which are a kind of Crustaceous Arachnida. 
In the class Arachnida, I only comprehend the Arachnides palpistes of Lamarck, 
and which thus constitute a group well characterized, both internally [from the struc- 
ture of their respiratory apparatus] and externally, from their being destitute of antennae, 
and have ordinarily four pairs of feet. I divide this class into two orders : namely, the 
Pulmonaria and Trachearia. 
The class of Insecta is characterized in a very simple manner by the system of res- 
piration consisting of two air tubes running along the sides of the body, furnished at 
intervals with centres of ramifications, corresponding with the [external] spiracles, and 
by the possession of iwo antennae. The primary groups of insects are founded upon 
